The present invention pertains to a respiration humidifier with an outer jacket, a water feed, a breathing feed line and a breathing gas drain line. A bundle of hydrophobic hollow fibers made of a material that is permeable to water vapor but is impermeable to water is positioned inside the outer jacket. The breathing gas feed line and breathing gas drain line are in flow connection with the interior of the hollow fibers.
Respiration humidifiers are used to humidify the inspiratory air of respirators to physiological values and to optionally beat it. Such devices, which operate according to various principles, are arranged, in general, separated from the respirator.
One drawback of the separate arrangement for the user is the lack of clarity of handling, due, among other things, to the large number of different tubing and connections. If a humidifier is integrated within the respirator, the diversity of accessories and ultimately the overall costs can be reduced for the manufacturer, because a completely equipped respirator is offered.
A respiration humidifier of this class has been known from U.S. Pat. No. 3,871,373. One drawback of this respiration humidifier is the relative size as well as the additionally necessary components, such as pumps, feed and drain lines.
The object of the present invention is to propose an improved, compact and low-maintenance respiration humidifier of a simple design. The object is accomplished by means of hollow fibers having means for electrical heating on their outer circumferential surface.
One essential advantage of the present invention is that due to the compact, modular design, the respiration humidifier according to the present invention can be directly integrated in the inspiratory line of the respirator. Another advantage of the present invention arises from the fact that hygienically objectionable contamination of the breathing air can be avoided due to the closed water system. For feeding in water, a water bag containing sterile water is simply connected, and the static pressure of this bag fills the module according to the present invention with water.
For example, an intubation kit commonly employed in hospital practice may be used as the supply line. The water connection to the modular respiration humidifier according to the present invention can be designed such that a bacteria filter is arranged at the inlet, so that microorganisms cannot enter even if the water bag is not connected.
The respiration humidifier according to the present invention is designed as follows. A bundle of hollow fibers arranged essentially in parallel, preferably made of one of polytetrafluoroethylene (PTFE), polyurethane, polysulfone, and porous sinted glass, is located in an outer jacket, e.g., one made of a laminated plastic, the length and the diameter of the fibers being selected to be such that a water vapor-permeable area of about 500 to 800 cm2 is available in the circumferential area in the case of a corresponding number of fibers. The porous sintered glass can be hydrophobized with silicone. In the case of a fiber diameter of 1 to 2 mm, about 200 fibers with a length of about 65 mm are needed in order not to generate an excessively high flow resistance, and in order to obtain the most compact design possible with the desired humidifying capacity. A suitable flow expansion, which is directly in flow connection with a breathing gas feed line and with a breathing gas drain line into and out of the respiration humidifier, is located in the beginning and end areas of the hollow fibers. The water-filled outer area around the hollow fibers, which is in flow connection with the water reservoir via the water feed of the module, is located around the hollow fibers, and is closed by the outer, laminated jacket.
The hollow fibers themselves consist of hydrophobic or hydrophobically coated membranes, preferably ones made of PTFE, which let water through in the form of water vapor, but retain liquid water under the given conditions of use. After the water reservoir has been connected and the volume around the hollow fibers has been filled with water due to the static pressure, the entrapped air can flow out of the respiration humidifier via a separate ventilation, e.g., one made of porous PTFE, unless the hydrophobic hollow fibers exert a sufficient ventilating action themselves. The hollow fibers used make it possible to passively establish a nearly constant humidification of the air fed in the range of 90% to 100% relative humidity over the broad range of flow conditions. This means that the flow of gas is always humidified uniformly in continuous operation and in intermittent operation. It is essential for the present invention that the heater is arranged directly around the hollow fibers in the water bath in the jacket of the respiration humidifier, i.e., it is integrated in the humidifier module. It was found that the heat must be fed in as close as possible to the area in which the evaporation is generated. The evaporation takes place in this case on the inside of the hollow fibers on the gas/air side.
The basic objective of the present invention is to operate all hollow fibers at the same temperature in order to obtain an extensively uniform breathing gas temperature and humidity over the entire cross section of the humidifier module. Only this can guarantee an optimal utilization of every individual hollow fiber in terms of the release of humidity and heat. Individual hollow fibers might otherwise be too cold and would have an insufficient humidification capacity, whereas others would be too warm and thus they would lead to excessive humidification capacity, as a result of which the humidity would again precipitate as a condensate. Each hollow fiber of the bundle is directly heated electrically according to the present invention. This can be done in the following ways. Individual resistor wires are wound around the hollow fibers and in the longitudinal direction, or they are printed on or applied as strips or films, and, as an alternative and preferably, the hollow fibers are preferably coated from the outside by vapor deposition with a metal used as a resistor heater, and are provided with corresponding current connections. According to another variant of the preparation, the hollow fibers would be arranged on a heating foil in parallel and next to each other. The strip thus equipped would then be rolled up, so that a hollow fiber bundle with direct heating of at least part of the opposite circumferential surface areas of the hollow fibers is formed. The system is operated in practice such that a temperature range of about 40xc2x0 C. to 45xc2x0 C. is not exceeded, so that short-term bursts of hot gas, which are sometimes possible in prior-art humidifier systems, are ruled out. For a precautionary disinfection or sterilization, the entire humidifier module can be briefly heated by the integrated heater to a desired temperature, e.g., to 134xc2x0 C. for 3 minutes.
A temperature sensor may be introduced into the water bath for a desired temperature control. This may also be used at the same time to recognize lack of water and a possible overheating that may occur as a result. A possibly desired heater of the airway tubes with temperature control can be operated independently from the humidifier module. Setting of the desired humidity can be performed with this tube heater, which was also used in the prior art. If, e.g., the temperature is higher at the end of the inspiration tube than at the beginning, the relative humidity is reduced. The setting of the desired breathing gas temperature may also be performed directly from the respirator, and the measured values are indicated there. The control and the supply of the humidifier module with the correctly metered thermal energy may also be provided on the respirator, so that the respiration humidifier according to the present invention can also be integrated in a respirator functionally, not only due to its compact, modular design.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.